Yeah I found a wiring diagram and I have the haynes manual.
Well done on finding that, as stoney said, a bad earth can cause very odd symptoms.
It would be a good idea to carry on looking, its certainly a very strange fault you have and being intermittent doesn't help.
Good luck and let us know how it goes.
I haven't tracked down a wiring diagram for your model yet, don't suppose you have a haynes manual for it ?
I'm going to have a look at the weekend see if I can see anything else that may cause an issue and reseal all the lights with sealant. Hopefully it wont happen again and I can relax.
Thanks for your help I wouldn't have checked if it wasn't for your post.
I agree Stoney I hope it was.